A known control portion of a child-lock mechanism which performs changeover between a locked and an unlocked condition of a door of a vehicle is formed into a projection that can be moved left and/or right and is exposed to the outside of the door through an opening formed in the inner metal sheet of the door. The opening is shaped into an elongate hole so that the projection can move therein. Due to this construction, a wide gap is created between the control portion and the opening, and foreign matters such as dirt, dust, rainwater and so forth that accumulate inside the door get out of the door through this gap, and these foreign matters sometimes make the outer surface of the door dirty.
In addition, the control portion outwardly protrudes from the opening by substantially 1 cm, and due to this, a passenger's dress sometimes catches on the projection when he/she gets in and/or out of the vehicle.